Patent GB-421015-A (GB)
Title: Manufacture of photographic sensitisers
IPC: G03C1/14
Filed: 1933-05-05
Abstract: Sensitizing dyes are prepared by condensing with an ester of orthoformic acid or of an alkyl, aryl or aralkyl substitution product thereof or with a 2-iodoquinolinium salt a quaternary ammonium compound of a 2-methylbenzthiazole, substituted in the benzene nucleus by a thioalkyl, thioaralkyl, selenoalkyl, or selenoaralkyl group.  The dyes correspond with the general formula <FORM:0421015/IV/1> wherein r stands for alkyl, R1 or both R1 and R2 stand for thioalkyl, thioaralkyl, selenoalkyl, or selenoaralkyl, X for an acidic radicle, n for 1 and Y for --CH=CH--, or n for 3 and Y for sulphur; when n stands for 3, the hydrogen attached to the central carbon atom of the trimethine chain may be replaced by alkyl, aralkyl or aryl.  In examples: (1) 6-meththio-2-methylbenzthiazole diethylsulphate (prepared by treating the diazotized 6 - amino body with xanthic ester, saponifying and alkylating with dimethylsulphate and diethylsulphate in succession) is condensed with triethylorthoformate in pyridine; (2) 6-methseleno-2-methylbenzthiazole ethiodide (from the diazotized 6-amino compound by reaction with potassium selenocyanide, saponifying and reaction with dimethylsulphate and ethyliodide in succession) is reacted with triethylorthoformate in pyridine; (3) 5-ethseleno-2-methyl-benzothiazole ethiodide is reacted with 2-iodo-6-methylquinoline ethiodide in alcoholic sodium ethylate; (4) 6 - methseleno - 2 - methylbenz - thiazole ethiodide is condensed with triethyl-orthoacetate and triethylorthopropionate in pyridine; (5) 5-methoxy-6-meththio-2-methylbenzthiazole (prepared by converting 1-chloro-2-methoxy-4-nitrobenzene to the disulphide by the action of sodium disulphide, methylating to give 1 - meththio - 2 - methoxy - 4 - nitrobenzene which is reduced and converted to the thiazole according to Fries's method) is condensed with p-toluenesulphonic acid ethyl ester and condensed with triethylorthoformate in pyridine; (6) 2 - methyl - 5 - thiobenzylbenzthiazole (prepared by treating the 5-diazo body with potassium xanthate, saponifying and alkylating with benzyl chloride) is converted to a quaternary salt by reaction with ethyliodide and condensed with triethylorthoacetate in pyridine. Specifications 418,745 and 420,971 are referred to.  The Specification as open to inspection under Sect. 91 comprises also a manufacture of sensitizing dyes by converting to a cyanine dye according to a known general method a quaternary ammonium compound of a heterocyclic base having a fused-on benzene-ring substituted by a thioalkyl, thioaryl, thioaralkyl, selenoalkyl, selenoaryl, selenoaralkyl group.  The dyes are assigned the general formula <FORM:0421015/IV/2> wherein Y and Z stand for oxygen, sulphur, selenium, --CH=CH--, or --CR<1>R<11> (R<1>R<11> stand for alkyl or aryl), r stands for alkyl, R1 and R2 for thioalkyl, thioaryl, thioaralkyl, selenoalkyl, selenoaryl, selenoaralkyl, X for an acidic radicle, and n for 1, 3, 5 or 7; in the case of polymethene dyes the central carbon atom of the chain may be replaced by alkyl, aralkyl, or aryl and the lateral carbon atoms of the chain by alkyl radicles. Reference is made to the production of the substituted heterocyclic bases, the quaternary ammonium compounds of which are starting materials, by diazotizing the corresponding amino body, treating with xanthic ester or potassium selenocyanide, saponifying and alkylating &c. the product.  This subject-matter does not appear in the Specification as accepted.